Heat exchange apparatus



June 28, 1960 E. B. STONEBURNER 2,942,858

HEAT EXCHANGE APPARATUS Filed April 21, 1958 FIG. 3

INVENTOR. EDWIN 8. STONEBURNER ATTORNEY United States Patent HEAT EXCHANGE APPARATUS Edwin Stoneburner, East Moline, 111., assignor to American Air Filter Company, Inc., Louisville, Ky., a corporation of Delaware Filed Apr. 21, 1958, Ser. No. 729,878

3 Claims. (Cl. 257-306) This invention relates to heat exchange apparatus and more particularly to improved heat exchange apparatus of the type which utilizes a fluid such as steam to heat a medium such as air.

' For a number of years heat exchange devices have been known which have included outer conduit arrangements over which a medium to be heated can be passed, the outer conduits each'having disposed therein an inner conduit connected to a steam supply source. In some of these outer-inner conduit heat exchange arrangements, the inner conduits have been provided with open ends to permit the steam to pass to the outer conduits, the inner conduits often being provided further with spaced holes therealong in an attempt to obtain uniform steam distribution along the length of the outer conduits in order to avoid condensate freezing problems. In this latter arrangement, however, the pressure differential between inner and outer conduits has been so small that the great majority of the steam has flowed out the ends of the inner conduits. When the demand on such an arrangement has been high, the resulting flow pattern has been of little consequence since the outer conduits have been flooded with steam. On

the other hand, when the demand on this arrangement has been low, only a small portion of steam flows with unde sirable hot spots occurring at the open ends of the inner conduits.

In still another long known outer-inner conduit arrangement for heat exchange devices, the ends of the inner conduits opposite the ends connected to the steam supply source have been closed or capped and steam has been forced into the outer conduits through a plurality of spaced holes positioned along the lengths of the inner conduits. To obtain desirable steam distribution in this arrangement, it has been necessary to maintain the spaced holes in the inner conduits as ones of small cross-sectional area at the sacrifice of the total capacity of the heat exchange apparatus.

The present invention recognizes the numerous disadvantages of past outer-inner conduit heat exchange a'rrangements and eliminates these disadvantages to provide an outer-inner conduit type heat exchange structure which has desirable steam distribution characteristics over a broad range of operations to avoid'condensate freezing problems. Further, the present invention provides a structure withouta restriction in the total capacity of the unit. Moreover, the present invention provides a heat exchange structure which operates with a rise of entropy in the face of a rising demand thereon, which is straight forward and economical in its construction and operation and which can be efiiciently and readily serviced.

Various other features of. the present invention will become obvious to one skilled in the art upon reading the disclosure set forth herein.

More particularly, the present invention provides a heat exchange apparatus comprising a header including a steam supply section and a steam condensate discharge section, a plurality of spaced outer conduits over which a medium to be heated can be passed, each of the outer conduits 2,942,858 Patented June 28, 1960 having one end thereof communicating with the discharge section of the header and having extending longitudinally therein an inner conduit providing a passage therebetwecn, each of the inner conduits having one end thereof communicating with the steam supply section of the header and the'other end closed, a plurality of small steam distributing orifices spaced along the lengths of each of the inner conduits to provide efiicient steam distribution during low demand operation of the heat exchange apparatus, and steam release means cooperating with each of the inner conduits to release additional steam into'the outer tubes at high demand operation of the apparatus.

It is to be understood that various changes can be made in the arrangement, form, and construction of the apparatus disclosed herein without departing from the scope or spirit of the present invention. 7

Referring to the drawing which discloses one advantageous embodiment of the present invention:

Figure 1 is a diagrammatic elevational view, in section, disclosing the outer-inner conduit heat exchange device with the inventive improvement, during low flow operations;

Figure 2 is a diagrammatic elevational view, in section, similar to that of Figure 1, disclosing the apparatus during high flow operations;

Figure 3 is a broken, partial plan view, disclosing a portion of the inner conduit of Figures 1 and 2.

Referring to the drawings in detail, Figure 1 discloses the improved heat exchange apparatus as including a main header portion 3 sealed at one end 4 and having its interior divided by a longitudinally extending wall 6 to provide a steam inlet header 7 and a condensate discharge header 8. Inlet header 7 is connected opposite sealed end 4 to a source of steam (not shown) and discharge header 8 is connected opposite end 4 to a suitable condensate sump or return piping (not shown). Connected to condensate discharge header 8 in direct communication therewith are a plurality of outer conduits 9, these outer conduits being provided with closed ends 10. As is known in the art, the outer conduits 9 have mounted thereon in a rigid manner the heat exchange fins 11.

Disposed within each of outer conduits 9 is an inner conduit 12, one end of each of the inner conduits being connected to the steam inlet header 7. The outer diam} 'eter of each of the inner conduits is less than the inner diameter of the outer conduit with which it is associated so as to form an annular passageway 13 therebetwecn, a ring shaped perforate spacer member 14 being provided in the passageway between the inner and outer conduits to hold the inner conduit in proper position. As will be seen hereinafter, the passageways 13 receive steam from the inner conduits 12, the steam condensate passing off to the condensate discharge header 8.

; Each of the inner conduits 12 is provided with a plurality of small holes IS spaced along the length of the conduit; and, opposite that end of the conduit 12 which is connected to the steam distributor inlet header 7 is a steam release means broadly designated by reference numeral 16. This steam release means constitutes one of the principal features of the present invention. In the advantageous embodiment of the invention disclosed, the steam release means includes the pipe fitting 17 which is integrally attached in some suitable fashion such as welding with the inner conduit 12. Each of the fittings 17 is provided with at least one aperture 18 which advantageously can be shaped in the form of an elongated slot. In the embodiment disclosed, each fitting 17 is provided with two such apertures 18, one on either side of the fitting. The end of each of the fittings opposite that end connected to the inner conduit is provided with a seal member 19 integral therewith, the member 19 serving to seal ofi steam flow from such end. In this connection, it is to be noted also that seal 19 is of a cross-section corresponding to the inner cross-section of outer conduit 19 the seal serving as a further support for inner conduit 12 to hold the Same in proper position within outer conduit 9. a, Each oi -fittings 17 is tappedtas at 21 (Figure 3) so as tobe table to receive screws 24 therein. Toclose off apertures 18 of each of the fittings, there isprovided for each aperture a resilient valve means in the form of a reed member 22. This member can be made from any one of atnumber of suitable resilient metal materials of corrosio'n resistant nature. One end of the reed is maintained free to cover aperture 18 and yieldabley seal it off from passageway 13. The other end of reed 22 is held in place by a facing plate 23 superimposed over the end of member 22 and held in place by the'screws 24 engaging in tapped holes21. 7 p I It is to be understood that reeds 22 can be of different masses so that each reed will have a different natural frequency, thus avoidingtany undesirable vibration at like frequencies with resulting singing. It further is to be understood that, if desired, a number of steam release means similar to that described above can be provided along the length of each of the inner conduits. Fnally, it is to be understood that the reeds can be designed so 'as to be of sufiicient thickness to maintain the apertures closed belowany one of a number of preselected pressure points and to yield only at pressures above such a preselected point so as toopen the apertures 18 into communication with conduits 9.

In a typical embodiment of the invention, a heat exchange apparatuscan be provided, with outer conduits having /8 inch inner diameter and the inner conduits having inch outer diameter. Holes spaced at two inch centers along the length of the inner conduits can measure approximately 3 inch across to insure effective steam distribution in the outer conduit at low operating levels, such eifective steam distribution being insured even when the flow rate of steam is as low as 0.5 pounds per hour. Covering the apertures in the steam release means, which apertures can measure inch in length and M4 inch across, can ,be a resilient brass or stainless steel reed of .015 inch thickness. The reed can be engineered so as to yield at a predetermined pressure differential between the'inside of conduit 12 and the annular passageway 13 and, in the typical embodiment described,a setting of .5 p.s.i. can be used; Thus, when the flow rate of steam is increased during higher operating demands, the reeds are forced open and steam is allowed to escape through the apertures. It is to be understood that the yield pressure point for the reed can be set high enough so that the distribution pattern will remain constant even through the reeds are open. It further is to be understood that the present invention is not restricted to the dimensions and pressures as set forth 7 ,of steam and being'closed at the other end, a plurality of continuously opened small steam distributing orifices spaced along the length of said inner conduit to provide efiicient'steam distribution during low demand operations of said apparatus, and a steam release aperture adjacent the closed end of said inner conduit, said aperture having cooperating therewith a resilient valve means to maintain said aperture closed during low demand operations of said heat exchange apparatus when the pressure differential between said inner and outer conduits is below a preselected pressure point and to release steam therethrough upon high demand operations when the pressure differential between said inner and outer conduits rises above said preselected pressure point.

2. A heat exchange apparatus comprising a header including a steam supply section and a steam condensate discharge section, a plurality of spaced outer conduits over which a medium to beheated can be passed, each of said outer conduits having one end thereof communicating with said discharge section of said header and having extending longitudinally therein an inner conduit providing a passage therebetween, each of said inner conduits having one end thereof communicating with said steam supply section of said' headerand the other end closed, a plurality of continuously opened small steam distributing orifices spaced along the length of each of said inner conduits to provide efiicient steam distribution during low demand operations of said heat exchange apparatus when the pressure differential between said inner and outer conduits is below a preselected pressure point, and steam release means cooperating with each of said inner conduits to release additional steam into said outer conduits at high demand operations of said apparatus when the pressure difie renti-al between said inner and outer conduits rises above said preselected pressure point.

3.;A heat exchange apparatus comprising a header including a steam supply section and a steam condensate discharge section, a plurality of spaced outer conduits over which a medium to be heated can be passed, each of said outer conduits having one end thereof communicating with said discharge section of said header and having the other end closed, inner conduits extending longitudinally into each of said outer conduits and forming-an annular passageway therebetween, each of said inner conduits having one end thereof communicating with said steam Supply section of said header and the other end closed, a plurality of continuously opened small steam distributing orifices spaced along, the length of 'each of said inner conduits to provide efficient steam distribution during low demand operations of said heat exchange apparatus, steam release apertures adjacent the closed ends of said inner conduits, and resilient reed members cooperating therewith to maintain said apertures closed during low demand operations of said heat exchange apparatus when the pressure ,difierential between said inner and outer conduits is below a preselected pressure point and to release steam therethrough at high demand operations when the pressure differential between said inner and outer conduits rises above said preselected pressure point.

- UNITED STATES PATENTS 7 2,229,032 Ashley Jan. 21, 1941 2,463,996 'Polk Mar. 8, 1949 2,611,584 Labus Sept. 23, 1952 

